I guess it depends on the region...
Our local operator lists the following 4G frequencies(MHz): 800/ 850/ 900/ 1800/ 1900/ 2100/ 2600 Source (in estonian)
However, when you compare the phones, you'll see that Xperia X is in many characteristics more "high tech" than Xperia XA2: GSMArena comparison
Xperia X just have two versions... Single and double sim... Xperia XA2 have various versions for differents regions... I have the USA/Canada/Latin American version that have differents frequencies that you listed (as for example band 4 (1700/2100/ that use my operator for LTE in my country). Apart of that, I think that nothing more varies from the European version